At slaughterhouses a classification of the individual cattle carcasses is made in order to establish a price between the farmer and the slaughterhouse which is in accordance with the quality of the carcasses. A skilled classification expert appraises the conformation and fat cover of the individual carcasses and fixes their category. The expert then grades the carcasses in accordance with a classification system.
The system applied within the EEC comprises five classes of conformation designated E, U, R, O and P. In order to be given an E classification the carcass must have an excellent conformation and be without defects in respect of its essential parts. All profiles must be convex to super-convex, and the muscles must be exceptionally developed. The round must be very rounded, and the back wide and very thick, up to the shoulder which must be very rounded.
The grades U, R, O, and P are awarded less valuable carcasses. Thus, the grade P (poor) is given for carcasses with profiles which are concave to very concave and with muscles which are poorly developed. In these carcasses the round is poorly developed, the back is narrow with visible bones, and the shoulder is flat with visible bones.
In order to achieve a higher differentiation in the fixing of the price each class may be divided into three sub-classes. Thus, the grade E- denotes a carcass graded in the lower third of the class E, whereas the grade E+ denotes a carcass in the top third.
The system includes five classes of fatness, 1 to 5. Grade 1 is given for carcasses without or with a low fat cover, and without fat within the thoracic cavity. Grade 5 means that the entire carcass is covered with fat and that there are heavy deposits of fat in the thoracic cavity. The round is almost completely covered with fat, so that the seams of fat are no longer clearly visible. In the thoracic cavity the muscle between the ribs is infiltrated with fat.
Cattle carcasses which represent the extreme grades of the scales can fairly easily be distinguished from each other. On the other hand, great experience is required to make a sure classfication of carcasses which differ from each other by one step on the scale. This is particularly true for carcasses which are graded in the intermediate classes, where good and poor properties are present in a mixture, and these must be weighed against each other. Unfortunately, the situation is that the majority of the carcasses occur in the intermediate classes. This means that the classification may be uncertain, with a risk that the prices are fixed on a wrong level.
Another thing is that the class only to a certain extent reflects the value of the carcasses. The classification must be considered as a rough division of the carcasses into various groups only, which may each, by experience, represent a price category. The same class may quite well include carcasses with different composition as regards lean, fat and bone, and consequently with different prices per kg.
The exact value of the individual carcass can only be fixed by dissection of the carcass and assessing the individual cuts. A substantial effort of work and assessment is required, which is not possible for practical reasons. Among the qualities which influence the value of the carcass may be mentioned: the yield of saleable meat, distribution of meat of the carcass, the content of fat of the carcass, muscular volume, colour of the meat, colour of the fat, marbling, tenderness and taste.
A need exists for a semi or fully automatic method which may replace the above mentioned subjective classification procedure by a sure, objective classification of cattle carcasses. If possible, the method should also provide information about other properties of the individual carcasses which affect the value of the carcasses.
In a publication is described an attempt to provide an objective classification of cattle carcasses by means of video recording. (S. E. Sorensen: "Possibilities for Application of Video Image Analysis in Beef Carcass Classification" in In vivo measurement of body composition in meat animals, Elsevier (1984), p. 113-122). The carcass is positioned in front of a video camera on a dark background and a video picture is registered and the gray values stored in a memory. By processing the values in a computer system the boundary of the carcass is determined. Different parameters, such as width of the breast, waist, thigh and carcass area may be calculated on the basis of the boundary, and it is suggested that the conformation and lean/bone ratio may be estimated if the parameters are used in a formula obtained by regression analysis.
Likewise, the gray value distribution within the carcass boundary may be calculated and it is suggested to estimate a class of fatness by using the result in a formula obtained by regression analysis.
In the publication it is mentioned that the application of video image analysis for carcass grading is far from simple and several potential problems are to be considered. It is concluded that a thorough optimization of the analysis procedures is required and for optimal performance the method might have to include the third dimension.
It is known to classify pig carcasses by means of weight of the carcass and some measures of meat thickness and fat thickness. They are converted into a meat-percentage which is used for the fixing of the price. The thicknesses are measured by means of an instrument with a probe which an operator inserts at certain places of the carcass.
Furthermore, it is known to measure the meat and fat percentage of cattle carcasses by means of said instrument. However, an objective classification of cattle in accordance with the systems valid today cannot be performed in this way, as there does not exist any usable correlation between such measurements of thickness and classes.
In the patent literature various methods have been suggested to provide results of measurements which can reflect quality properties in individual pig or cattle carcasses and which may be used as a basis for an objective classification.
French Patent No. 2,546,423 describes an apparatus designed for automatic measuring classification parameters of cattle carcasses. The apparatus comprises an arrangement with a frame having a supporting surface for a split cattle carcass. A complicated mechanical system with mechanical sensors measures the essential dimensions of the carcass. This apparatus requires a high degree of maintenance of the mechnical parts, and the veterinary authorities may demand a sterilisation of every sensor between each measurement. The apparatus is not capable of determining the class of fatness or the composition of cattle carcasses.
West German Patent No. 27 28 913 describes an apparatus for the classification of pig carcasses in accordance with the system used in West Germany.
The apparatus comprises a dark chamber provided with a colour video camera and some daylight sources. A split pig carcass is placed in the chamber in such a way that the cut surface is facing the camera and the light sources. Parameters of the cut surface, such as the meat and fat thicknesses are determined by means of the camera and processed in a micro processor system. The camera registers the wall of the chamber as black, the fat as white and the meat as red. In this way the camera differentiates the different materials.
Based upon the recording and the weight of the carcass the class of quality may be calculated in the computer of the apparatus, and a mark denoting the class is automatically applied to the carcass by means of a stamping device.
French Patent No. 2,545,010 also describes an apparatus for the classification of pig carcasses. In this apparatus the height of an ultrasonic probe is set by means of a video recording of the cut surface of a split carcass. Furthermore, the recording of the camera is used for the determination of thicknesses in the cut surface. These thicknesses and the ones determined by the ultrasonic probe are used in the calculation determining the class of the pig carcass.
Thus, the literature has proposed different methods in which a video recording is used in the semi or fully automatic classification of carcasses, but no one has provided a method for the classification of cattle carcasses which is sufficiently accurate in practice to determine the composition and the conformation class as well as the class of fatness in an objective way. Such a method would be very difficult to provide in comparison with the current objective classification of pig carcasses in which it is sufficient to determine a few thicknesses of meat and fat. Even within the same category cattle carcasses may be very heterogeneous.
Furthermore, the thicknesses of meat and fat may not always be determined by means of a video recording of the cut surface of the carcass because some slaughterhouses do not split carcasses until after the classification procedure.